# How to Find the Length of a JSON Array in PostgreSQL?

> In PostgreSQL, a built-in function named “JSON_ARRAY_LENGTH()” is used to determine the length of a JSON array.

PostgreSQL provides a **JSON** array data type that helps us store ordered collections in JSON format. JSON arrays are similar to standard arrays in programming. They are enclosed within square brackets “[ ]” and can have different data types like strings, objects, numbers, etc. JSON arrays are optimized for PostgreSQL's database engine.

This post illustrates a comprehensive guide to finding the length of the given JSON array.

 **How to Find/Fetch the JSON Array Length in Postgres?**

In Postgres, a built-in function named “ **JSON_ARRAY_LENGTH()** ” is used to calculate/determine the length of a JSON array. The retrieved length represents the total number of elements in that particular JSON array.

 **Syntax**

Use the below-stated syntax to retrieve the length of a JSON array using the JSON_ARRAY_LENGTH() function:
    
    
    JSON_ARRAY_LENGTH(array JSON);

 **Parameters**

The stated function accepts a single argument “array” that represents a JSON array.

 **Return Value**

The stated function retrieves the length of the given JSON array.

 **Return Type**

It retrieves an **INTEGER** value which indicates the length of the specified JSON array.

 **Example 1: Finding the Length of a JSON Array in Postgres**

The below code snippet demonstrates the use of the JSON_ARRAY_LENGTH() function in PostgreSQL:
    
    
    SELECT JSON_ARRAY_LENGTH('[100, 110, 90, [120, -12]]');

The stated function retrieves the length of the specified array:

 **Example 2: Finding the Length of a JSON Column in Postgres**

Let’s set up a sample table with the following structure:
    
    
    CREATE TABLE emp_table (
    emp_id SERIAL PRIMARY KEY,
    emp_data JSON
    );

Now execute the following query to insert new records into the “emp_table”:
    
    
    INSERT INTO emp_table(emp_data) 
    VALUES
    ('[100, 120, 30, 210, 1]'),
    ('["John", "Joseph", "Mike", "Johnson", "Miller"]'),
    ('[{"e_name": "John", "e_age": 28},
    {"e_name": "Johnson", "e_age": 32},
    {"e_name": "Joseph", "e_age": 27}]');

The desired records have been successfully inserted into the “emp_table”:

Confirm the table’s content by executing the following command:
    
    
    SELECT * FROM emp_table;

Now we will use the JSON_ARRAY_LENGTH() function to find the length of the “emp_data” column:
    
    
    SELECT emp_data, 
    JSON_ARRAY_LENGTH(emp_data)
    FROM emp_table;

The stated function successfully retrieves the length of the given JSON array:

That’s all about finding the length of a JSON array in Postgres.

 **Conclusion**

In Postgres, a built-in function named “ **JSON_ARRAY_LENGTH()** ” is used to determine the length of a JSON array. The retrieved length represents the total number of elements in that particular JSON array. The stated function accepts a single argument “array” which must be a JSON array. This post has illustrated the working of the JSON_ARRAY_LENGTH() function in PostgreSQL.

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